Hardened Earth
by Sage Thrasher
Summary: Adversity and strength are not reserved for ninja. A civilian can make just as much of a difference—for better or for worse. [OC-Insert]
1. Talc

_After the rain, earth hardens._ –Old Japanese Proverb.

* * *

**Chapter One: Talc **

* * *

The doctor's face was grave and ashen. Her footsteps fell with a finality that could only signal bad news.

"Oh god," cried the man, falling back into the chair. "Is…"

"I'm sorry," replied the doctor gently. "We were unable to save your wife. But we _were_ able to save your daughter."

He was silent for a few moments—though for him, it felt more like an eternity. "Can I see her?" he said, finally. "Can I see my daughter?"

"Of course." The doctor hesitated, and the man's shattered heart sunk lower. "We were able to save your daughter," she said again, "but… her chakra coils are completely shredded. The backlash of her mother's death was too much for her developing system."

"What do you mean?"

"Her involuntary chakra system works fine. Her cells will get the energy they need to survive. However, she will not be able to control her chakra at all." The doctor looked straight at the man. "It is absolutely impossible for her to become a ninja."

He bowed his head. "Is she otherwise healthy?"

"Perfectly so," said the doctor, smiling slightly. Many ninja would not have reacted the same way.

"Then I wish to see her." He pushed past the doctor and walked into the gray room where his daughter cried, feebly struggling against the blanket wrapped around her. His wife rested on the bed next to the crib. Gently, with uttermost care, he lightly brushed his finger against his wife's cold cheek for before pulling the blanket over her head. Then, the man ignored the nurse's protests and picked his daughter up.

Tears began to form in the man's eyes as he rocked his wailing daughter.

"Hello," he whispered. "Hello." He paused, composed himself, and called his daughter by her name for the first time. "Hello, Kumade."

* * *

Explaining what happened to his son was the hardest part.

"Mother died?"

"Yes, Sakumo." Tired, Hatake Shizu looked at his son. When had he grown so big? Sakumo had just turned seven, but he had already graduated, becoming a ninja and an adult in the eyes of the village—though not in the eyes of his father.

Sakumo rubbed his eyes, reflexively blinking back tears. "Moth—" his voice cracked. Taking in a shaky breath, the boy stepped forward. "Is that my sister?" he asked, voice wavering slightly.

The Hatake clan head nodded. "Her name is Kumade."

Sakumo cautiously prodded his sister with his finger. To his surprise, the baby grabbed it. The boy glanced up at his father with teary but surprised expression.

Shizu smiled. "Do you want to hold her?"

After thinking it over, Sakumo agreed. He held her carefully, as if she was made of glass.

"She's wrinkly," said Sakumo bluntly.

"She is." Shizu's smile grew slightly bigger. "All babies are wrinkly."

Sakumo scrunched his nose. "Weird."

"Weird," agreed Shizu.

Unconcerned with the conversation, Kumade quickly fell asleep.

* * *

The Hatake clan had always been a small one. But the First Great Shinobi War had hit the Hatake clan exceptionally hard, causing its numbers to dwindle further. Currently, it consisted of only three members: Shizu, Sakumo, and Kumade.

But regardless of their current state, the Hatakes _had_ once been a true ninja clan. The remaining members—at least, the two older ones—still possessed many of the traits that had distinguished them from other shinobi.

The silver hair was the most noticeable feature—second in fame to only to their prized white chakra. The clan also possessed a minor Dog Summoning Contract, which endowed them with keener senses and lifelong companions. In battle, the Hatake clan was known for their precise chakra control and their devastating kenjutsu style.

The combination of these abilities had made them particularly dangerous on the field. Though not influential or numerous, the clan was afforded respect for its skilled members.

A less known trait of the Hatake clan was its propensity for child prodigies. On average, Hatake children tended to be very smart when compared to their peers.

It was because of this that Kumade managed to avoid suspicion.

Whenever she did something that a normal child couldn't do, her father always chalked it up to Hatake genes. And that suited Kumade just fine.

_Damn it, Jim_. _I'm an engineer, not a child development specialist! _ Her lips quirked up at the thought. Thank God for crazy genes. She knew next-to-nothing about kids. Even by freaky magic ninja standards, she was an odd child—but her clan blood deflected further suspicion.

And that thought reminded her of something she'd rather forget.

She was in fucking _Naruto_.

And she knew _nothing_ about that show.

Oh, Kumade had read plenty of manga in her last life. (Side thought—reincarnation? Not cool. Traumatic, more like it.) She'd been a proud geek/nerd/whatever back then. But for some reason, magic ninjas had never really caught her interest. The length of the series had intimidated her, and she'd been more of a sci-fi fan, anyway.

Boy, was she regretting it now.

Thankfully, Kumade didn't need to worry about being a ninja herself. She didn't know the specifics, as her grasp on the language wasn't very strong, but something about her body made becoming a ninja impossible. Hooray for not becoming a murderous child assassin!

That didn't mean no training, though. Despite being (basically) a chakra-less five year old, Kumade's father still drilled her in sword fighting. She'd be useless against anyone with a tiny bit of chakra control, but her father's goal was to make her stronger than most other civilians.

But Kumade knew that she got off easy. Her older brother trained four times as much as she did. She _really_ didn't envy him.

"Watcha doing, squirt?" Her previously mentioned brother ruffled her ridiculous hair. "You look like you're thinking too hard."

"Thinking too hard is better than not thinking at all," she snipped back, grinning. "How was your mission?"

The twelve year old smirked. "Same old, same old. We had to do another stupid D-rank because Juro broke his leg while training." He shuddered. "We had to catch this demon cat…" Sakumo chattered on, using wild hand gestures to punctuate his points.

Kumade laughed as she listened to her brother's exaggerated tale. "If you fought as well as you told stories, then no one would be able to win against _you_," she teased.

Sakumo stuck his nose in the air, and his voice took on an outrageous accent. "I'll have you know that I was the top student of my year. Clearly, I'm the best in every way possible."

Kumade raised an eyebrow. "I know you're trying to impersonate someone, but I have no idea who."

Her brother sighed. "Oh, right. I forgot that you don't know him." Sakumo stretched, causing his joints to pop. "There's this really stuck-up kid named Orochimaru. He's one year younger than me, but his ego's bigger than Konoha. It's annoying as he—er, heck."

"Right." She snorted. "Like _your_ ego's any better."

"Hey!" Sakumo ruffled her hair again. "Take that back!"

The two fell into easy banter that continued for a few more minutes. Then, Sakumo decided to be responsible—at least for a little bit.

"Since father's not home yet, I'll make you something to eat!" he said proudly.

"Are you sure? You managed to burn the soup the last time you tried to cook."

Sakumo clutched his chest. "Alas, your words are sharper than any kunai! You wound me, sister." He grinned slyly. "I see you live up to your name."

Kumade glowered at him. She knew it was Hatake tradition to have farm-related names, but why the hell had her father thought _pitchfork_ was a good name for a child? At least her brother's name was something nice and peaceful like _crops._ Really, there were very few things she hated more than her new name. Well, the child soldier thing was pretty bad too. Now that she thought about it, there were a _lot_ of things that Kumade hated about this place.

But it wasn't all bad. The technology level was about equivalent to the U.S. in the 1950s, so at least there were movies and entertainment. The chakra-magic was pretty cool, even if she couldn't use it. And of course, there was her brother Sakumo.

Kumade closed her eyes as she thought about it.

She'd had a younger sister during her past existence. Being just one year apart, they'd argued like cats and dogs. But their bond had been stronger than steel.

Her relationship with Sakumo was different—but equally as close. It was nice being the younger one, for once. They had a friendly, playful bond. Sure, Sakumo could be a bit overprotective, but it was only to be expected. In the ninja world, she was defenseless. Plus, she was five. His paranoia was completely excusable.

"Ready!" Sakumo plunked down a plate with a sad-looking sandwich.

"Really?" She prodded the soggy bread and lettuce.

"…you don't like it?"

She sighed and took a bite. "It's awesome," she lied through her teeth. Kumade shoved the rest down her throat. "I'm done!"

"See? I _can_ cook!" Sakumo smiled proudly.

"Right." She coughed then grinned as she remembered something. "Sakumo-nii," she said, voice becoming saccharine-sweet. Sakumo immediately narrowed his eyes. He knew that she only used that tone when she wanted something. "Did you bring the textbook I asked for?" asked Kumade, eyes wide.

"Uh… no?"

Kumade pouted. "Why not?"

"I forgot," he laughed sheepishly. "Why do you want my old math textbooks anyway?"

"Because math is the _greatest_," she replied reverently. Math had been her love, and she'd be damned if she forgot any of it. Once she worked her way through the basic algebra textbooks, Kumade could ask for the more advanced ones without attracting suspicion.

"Weirdo," he scoffed. Sakumo was excellent at math—he'd graduated at the top of his class, after all—but he didn't have the fanatic love that his sister seemed to have.

"Thanks." She rolled her eyes and glanced at the clock. "When did your sensei want you back again? It's almost two."

Sakumo dropped his sandwich. "Shi—ship," he corrected hastily. "Koharu-sensei's going to _kill_ me! Lunch break was over ten minutes ago!" He rushed out of the room, food forgotten.

Kumade sighed and leaned back. Her brother could be so forgetful, despite being a ninja. Quickly, she tossed the plates into the sink before heading to her room to practice the alphabet. For some reason, people here used a writing system with literally _thousands_ of characters. Despite being here for five years, she _still_ hadn't achieved complete literacy.

Her tutor had been effective, but it simply wasn't enough. Practice was equally necessary. (Being a member of a shinobi clan, even if she wasn't a ninja herself, Kumade had the advantage of a tutor. Civilian schools were for plebs.)

Her life here was… surprisingly boring. Her father and brother were often away due to missions, leaving her alone with only her father's ninken. Which were admittedly awesome. She wasn't fluent in "Dog" like her brother and father, but she was getting close.

Talking to dogs?

Awesome.

But other than that, five year olds couldn't do much. And she was bored. So, _kanji_ practice it was…

* * *

"You brought your little sister?" Juro stared at his teammate.

Sakumo stared back, confused. "Well… yeah. We're allowed to bring family, right?"

"You brought your _six-year old civilian _sister to the Chuunin Exams?"

"Is that bad?" Sakumo blinked.

Kato Mayu, Sakumo's other teammate, smiled in a rather strained way. "Yes, Sakumo. It's bad."

Kumade sighed. Apparently, this Chuunin Exam was a thing where preteens beat each other up to get a promotion. Her brother had made it through the first two stages, and now they were at the final one: the exhibition matches.

"Why's it bad? It's not dangerous for her. Only Konoha genin are allowed to participate, right?"

"Well, yeah…" Juro glanced at the annoyed child. "But isn't she… I dunno, a bit _young_ for this?"

"But she's smart." Sakumo shrugged. "I don't see what your problem is."

"It's fine," reassured Kumade. "I want to support my brother, anyway."

She'd gotten to know Mayu and Juro quite well in the past few weeks. The genin team had been training non-stop for the exams, and they'd often used the spacious and isolated Hatake Compound to practice. Kumade quite liked their company, even if they had a tendency to baby her.

"Fine," growled Juro. "If she gets nightmares, don't blame me."

The three genin suddenly stiffened and fell into attention as their teacher approached. The beautiful and powerful Utatane Koharu glanced at her three students. "You're next," she said to Sakumo. "You don't want to be late."

Sakumo paled and hurried to the side of the arena. Koharu turned to her remaining genin and Kumade. "You three should head to the stands if you want a good view."

After bowing sharply, Mayu and Juro ran to the stands. Kumade followed them, after politely greeting her brother's teacher. To be honest, she wasn't exactly sure what to think of the older woman. Koharu was polite enough, but she was also firm in a way that somehow got on her nerves. Oh well.

Thoughts about Koharu were soon forgotten as Kumade watched her brother fight. With a sort of horrified fasciation, Kumade watched Sakumo quickly defeat his Akimichi opponent by using a powerful lightning-charged attack.

"Are you ok?" asked Mayu, noticing Kumade's tightly clenched fists.

She laughed nervously. "Just worried for my brother." _Why are they doing this? It's.. savage. _She winced. _I really hope nobody dies. _

Thankfully, nobody did.

Juro was knocked out in the first round by an Aburame, while Mayu lost in the second round to a clanless kunoichi. Sakumo, much to Kumade's relief and amazement, managed to win the whole tournament.

"Isn't your big brother the best?" he crowed.

"I'm just glad you're safe," she mumbled, hugging her older brother. The tournament had reminded her that Sakumo would _actually be fighting_ and risking his _life_ as a ninja.

His eyes softened as he hugged her back. "Me too. It'd be bad if I got hurt. I'm too cool for that." Then, he pouted. "But you aren't going to congratulate me or anything?

"Congrats," Kumade replied belatedly. "Now let's go home."

* * *

Their father returned two days after Sakumo's promotion to chuunin. After he arrived, they had a small celebration. (Frankly, Kumade didn't think it was worthy of being called a celebration. It was too somber for that.)

"I'm proud of you, Sakumo." Shizu smiled at his son. "Though I'm sorry that I missed your exams." He cleared his throat as he placed a package on the table. "Sakumo, this is for you. From now one, you have my permission to use the Hatake kenjutsu on the field."

Sakumo bowed his head, uncharacteristically formal. "Thank you, father." Carefully, he unsheathed the tanto, revealing a gleaming white blade.

Kumade resisted the urge to whistle. The Hatake kenjutsu style was jealously guarded—tradition held that a student couldn't use it in battle until they were deemed worthy by their teacher. A great honor indeed.

"I won't let you down," murmured Sakumo.

Fondly, Shizu messed his son's hair. "I know you won't."

* * *

Hatake Shizu died exactly one week later. A simple scouting mission turned into an all-out battle that left him and his team dead. No one took responsibility for the attack, but it was a clear sign of the increased tension between the villages.

Kumade cared about none of this as she cried at her father's wake. Shizu had been slightly distant, but he'd loved and cared for her all the same. She hadn't always approved of his decisions concerning her and her brother, but that did not affect her affection for her second father in the slightest.

Sakumo stood silently beside her as people approached to offer their condolences. Both of his teammates, though extremely uncomfortable, had attended. One of Sakumo's younger friends from the Academy, a boy by the name of Jiraiya, had also attended. Other than that, the rest of the mourners were friends of their father.

The last person to approach was Sakumo's sensei—and their new guardian. With no living relatives, Sakumo (and by extension, Kumade) were to be under the care of Koharu until Sakumo turned fifteen or reached jounin. The gesture was more symbolic than literal. The two Hatake children would still be living in their compound alone, but the responsibility for their wellbeing fell to Utatane Koharu.

"It's time to go, children." Koharu's voice held genuine sympathy and understanding, though her tone was unyielding.

Sakumo followed his teacher without a backwards glance, but Kumade couldn't help but look back.

Her brother tugged on her arm, leaving Kumade no choice but to follow.

* * *

**AN: **Kumade is Sakumo's younger sister by seven years, making her roughly five years older than Minato and his peers. She will not become a ninja in any way, shape, or form. She will also not be useless.

This story is fairly slow building, and I plan to look at both the civilian and political sides of Konoha. There won't be too much action, as Kumade is a civilian, but there will be some.

(Honestly, I'm just testing the waters with this chapter. Please tell me what you think!) Thank you for reading, and I hope you enjoyed it!


	2. Graphite

**Chapter Two: Graphite**

* * *

"You smell sad." Ashi huffed once before cuddling closer to Kumade.

"That's because I am sad," she replied.

"Why?" The dog tilted his head and looked at her with soulful eyes.

She put aside her pencil and textbook. She'd lost her appetite for equations. Unfortunately, math wasn't a solution to all problems, particularly the emotional kind. Kumade sighed, gently petting the summons's fur. "Because dad's dead."

"Shizu-sama…" Ashi whimpered.

Taking comfort in his warmth, she scratched the dog behind his ears. Sakumo had started to leave a summon with her every time he left on a mission. Kumade knew that his teacher didn't like that—the older woman thought it was an unnecessary waste of Sakumo's chakra. To some degree, Kumade agreed. She was perfectly safe in the village. But on the other hand, Kumade was rather lonely.

For not the first time, she wished that she could summon members of the pack by herself. But her messed-up chakra system made that impossible.

_Although…_ Kumade's mind began to kick into gear. Over the past few weeks, she'd learned quite a bit about summoning from her brother and the dogs. Apparently, chakra was needed to anchor a summon to this dimension. To send a summon back, all you had to do was disperse the anchored chakra. Because the chakra used was a one-time thing and not a constant drain, any source of chakra was usable. The really important part was the blood. After all, the contract was tied to the personal chakra signature of a person's blood.

_So all I have to do is sign the contract and get an outside source of chakra. But where would I get the chakra from?_

A sharp knock at the door interrupted her thoughts. Kumade stood up from the table and went to answer it. Ashi jumped after her, sorrow forgotten. Kumade peered through the eyehole to see Jiraiya and another boy she didn't know.

"Great. Did Sakumo blackmail his friends into watching me again?" she grumbled. Sakumo, in his ever increasing paranoia, would badger his friends to check on her when he was gone. The visits ranged from pleasant to painfully awkward, depending on the friend in question. Jiraiya was one of the more entertaining ones, but he could be rather noisy.

Kumade glanced at Ashi. "Safe?"

"Safe," confirmed the dog. There was an ingenious seal on the compound door; it allowed scents to come through, but it prevented scents from coming out. It was like a one-way mirror, except for smells. There were also some other, more complicated security seals, but Kumade didn't know much about them.

She pressed her hand against the door to deactivate the seals. The markings glowed blue before fading. Kumade opened the door and called, "Come in, Jiraiya-san."

"Kumade-chan!" Jiraiya practically bounced inside. "It's good to see you!"

"Yeah, yeah." Kumade grinned. "I'm sure you really want to babysit me."

Jiraiya smirked back. "I'd love to babysit you, but alas!" He pressed his hand against his forehead and struck a dramatic pose. "I must train with my uncle. Though it pains me to leave you, I have brought you a substitute. A sucky substitute, but a substitute nonetheless."

"Oh really?" Kumade raised an eyebrow. "Who is this substitute?"

"He's right…" Jiraiya trailed off. "Hey! Orochi, why are you still outside?"

The pale teen gave a sigh. "The owner of the house hasn't invited me in yet." He gave both of them a pointed look, made more severe by his yellow eyes. "And don't call me Orochi."

Kumade blushed a bright red._ Stupid fair skin, telling everyone what I'm feeling._ "Uh… right. Well,

I'm Hatake Kumade—"

"Sakumo's sister, I know," he interrupted. "I am Yashagoro Orochimaru."

She scowled at him. First he acts all high and mighty, preaching about manners, and then he interrupts me. Sakumo was right about him. "Come inside."

Sneering, Orochimaru stepped inside. He walked slowly, and Kumade noted the bandages around his shoulder and side.

Jiraiya laughed sheepishly. "Anyway, Oro got injured on our last mission, so he can't train."

"And since your brother had the foresight to ask when Hiruzen-sensei was listening, I was roped into watching you," finished Orochimaru. "Don't call me Oro, either."

"Sure thing, Rochi!" Jiraiya sniggered. The other boy sighed and rolled his eyes.

Kumade cracked a smile. "So, Jiraiya-san, Rochi—I mean, Orochimaru-san, do you want anything to drink? Or eat?"

"I gotta go. But thanks!" With a jaunty wave, Jiraiya hopped out the door. "I'll see you both later!"

Orochimaru glared at her. "No," he said shortly.

"Suit yourself." Kumade walked to the table and sat back down. Wasting no time, she continued doing her math problems. Ashi curled by Kumade's feet and began to doze. Unsurprisingly, math bored the canine. After a moment of hesitation, Orochimaru joined them.

They sat in silence for five minutes. Kumade could feel Orochimaru watching her. Finally, his patience ran out—or, his curiosity got the best of him. "What are you doing?"

"Math."

Orochimaru scoffed. "Obviously. What kind of math?"

"Implicit differentiation. Just basic calculus." She decided to take pity on him. _I'd be bored if I was watching a kid do math problems_. Kumade turned her paper around. "See?"

He frowned slightly and peered at the paper. "What?"

"Didn't you guys do calc at the Academy?" she replied with an equally arrogant tone. Kumade knew that the ninjas-in-training didn't. Her brother's Academy textbook didn't go above basic geometry and algebra. But she felt like teasing the too-serious teen.

"No, we did not," he enunciated, drawing out every word. "That is why I am asking you."

"Well, it's simple. Differentiation is basically finding the slope of the tangent of each point. In a function, I mean. Well, only if the function is continuous and differentiable, which is something else. You know, the derivative? Which is how much a quantity changes?"

Orochimaru gave her a blank look. Kumade rubbed the back of her neck and cringed. Ok, I'm really not explaining this well.

"Um, let's start from the beginning." Kumade began explaining functions and slopes, and to her surprise, Orochimaru absorbed it like a sponge. Soon, they had worked their way up to the power rule.

"So, you subtract one from the exponent—"

"And multiply the original one to the coefficient," finished the teen with satisfaction.

Kumade raised both eyebrows, impressed. "Wow, you're pretty smart."

"Obviously." He looked at her for a long moment. "You are not entirely useless," said Orochimaru grudgingly.

"That's… not a compliment. We need to work on your compliments."

Orochimaru ignored her and continued working on the function. He showed her his work, and Kumade nodded. It was perfect. Orochimaru glanced at the problem before giving her a considering look. "Besides knowledge for knowledge's sake, what is the point of this math?"

Her mouth dropped open. "What? Did you just ask me what the point is?" She spluttered helplessly for a second. "Besides being plain awesome, calculus is only the most useful math ever! You can use it to find how fast something is changing, or how to build anything that isn't made of straight lines, or model three-dimensional shapes, or calculate the growth rate of bacteria!" Kumade threw her arms in the air. "Without calculus, you'd just be guessing! There'd be no precision, no accuracy!"

That piqued his interest. "The growth rate of bacteria?"

"Yeah, like cell cultures and stuff! You know, mitosis or something? It's exponential, usually." She scratched her head. "Don't ask me, I didn't—" Kumade cut herself off, "learn biology?" she finished weakly._ I can't talk about majoring in subjects. I don't think this world has colleges._

Orochimaru disregarded her blunder. "Cell cultures. Interesting." He moved on to the next problem, completing it with a focus he hadn't had before.

He must be a fan of biology. She shrugged and continued working. _He wasn't really interested until I told him about the cells. I wonder if he wants to be a doctor. Physics is better, obviously. But different people, different tastes._

"Do you know the relationship between chakra and this type of math?" he asked, interrupting her thoughts.

Kumade blinked. "Uh… no. I know pretty much nothing about chakra. I'm a civilian."

"But why?" He frowned at her. "You're certainly intelligent enough. And with your clan background, your success is guaranteed."

"I literally can't. I'm not sure about the specifics, but my chakra doesn't work." She shrugged as she puzzled out a particularly difficult integration with u-substitution.

He tilted his head, like a snake observing a particularly intriguing morsel. "Did you have this condition since birth?"

Kumade paused in her writing. "Yeah. It had something to do with my mom dying, I think."

"Then it's likely maternal backlash syndrome. The involuntary chakra system works, but conscious control of the refined chakra is near-impossible." Orochimaru nodded his head, satisfied.

She tapped her pencil against the table, and inspiration struck. After scribbling down the answer, Kumade gave Orochimaru her best puppy eyes. "Say, you know a lot about chakra, right?"

The teen suddenly looked uncomfortable. "Yes."

"And I know a lot about math." She smiled and edged closer to him. "How bout we make a deal? Since you're stuck babysitting me, I'll teach you more about math—if you teach me more about chakra. And I don't mean the basic stuff that civilians know. I mean the stuff you learn in the Academy. And the stuff that you've looked up."

A hint of puzzlement entered his voice. "Why do you want to know about chakra? You're incapable of using it."

Her smile grew wider, displaying her fangs. "Knowledge for knowledge's sake, if you will." _Heck yeah, I want to know about magic ninja voodoo!_ Her father had refused to teach her more than the basics, claiming that it was too dangerous. And Sakumo was too busy, nowadays.

He deliberated over her deal, and for a second, Kumade thought he was going to refuse. Then, his attitude did a one-eighty. "Of course," Orochimaru almost purred. He gave her a smile that looked almost predatory. "It will be a pleasure to work with you, Kumade-san."

* * *

For the next two weeks, Orochimaru came by at around ten in the morning. On good days, he'd greet her with a short hello—on bad days, he'd storm in and go straight to the textbook. He was a kind of moody teen, despite his brilliance. But learning new things seemed to have a calming effect on him, though. After about an hour of math, Orochimaru would return the favor by teaching her more about chakra. Despite his occasional rudeness, Orochimaru was an excellent teacher. Kumade admitted that he was now her favorite babysitter, if only because he didn't treat her like a little kid.

"… which is why you have to include y-prime," said Kumade as she finished explaining implicit differentiation.

"Simple enough." Orochimaru frowned at the paper. "I was thinking—"

"Wow, I knew you could do it!" she snarked. The teen shot her an annoyed look.

"As I was saying, I was experimenting with exponential functions. As you mentioned earlier, cell division does follow an exponential pattern." He began writing. "Let's say a hypothetical cell doubles every year. And if it were dividing for a year…" His writing grew faster. "Then I would have two cells at the end of the year. And four years the next, and so on." He sketched out a rough curve, neatly labeling the x- and y-axis like Kumade had told him to. "But an interesting effect happens if you treat cells like money. If cells divided based on interest… then you approach a limit!"

He continued explaining the odd effect of compound interest. After he finished, Orochimaru looked at her expectantly.

Kumade just stared with her mouth open. _What the hell? Orochimaru managed to independently come up with Euler's number! And he's been learning about equations for two weeks!_

"Well? What do you think?"

"I think you're a damn genius, and that depresses me," she said morosely. "The number 2.71828-whatever is known as Enmei's Constant." Of course, Euler's number wasn't named after Euler in this world, but math never changed, even if its names did. "It's one of the most important numbers in math, and you've figured it out by yourself."

For a second, Orochimaru looked startled. Then, a satisfied smile worked itself across his face. "Of course."

Kumade closed the textbook with a huff. "Your turn to teach me. I want to learn more about sealing. You said you'd tell me."

"You're quite demanding, you know?" His yellow eyes glinted in the light. Still, he pulled out his own dusty tome. "Sealing is a highly guarded art. You're lucky I even brought this book."

"Cut the shpiel, dude. I don't need to hear it every time." Orochimaru seemed to delight in making her beg for more sealing knowledge.

The teen gave her a look. "You say the strangest things."

"It's part of my charm." Kumade smirked. "So, what you got?"

"We were working on storage seals, correct? All seals do is store and release, whether it be energy, matter, or—"

"Yes, I know!" she said, exasperated. "Hurry up and get to the part about intermediate sealing arrays!

"So impatient, Kumade." He gave a put-upon sigh. "If you continue this attitude, I might decide to take my book and leave."

"Why, you little—"

The front door opened. "Kumade!" called a familiar voice. In walked Sakumo, disheveled, dirty but perfectly whole. "We managed to finish the mission a few days earlier, and—" Upon seeing Orochimaru, his carefree demeanor changed. His hand went to his sheathed tanto, and his eyes narrowed into slits. "What are you doing here?"

Orochimaru's attitude changed as well. He straightened and tilted his head, somehow managing to look down upon Sakumo despite being seated. "You asked me to watch your little sister, remember? Or are you incapable of remembering who you trust Kumade with?"

Sakumo looked ready to growl. "I asked Jiraiya…" His expression became sheepish. "Oh. Right." Then, fast enough to give her whiplash, Sakumo became angry again. "Wait. Kumade?"

Kumade blinked. Sometime after the first week, She'd stopped using suffixes with Orochimaru. He'd reciprocated, naturally. _The lack of suffixes means something important, doesn't it? That you're close friends, I think?_ Kumade wasn't really sure. She hadn't paid much attention to her tutor's etiquette lessons. Besides, she'd never used honorifics with her father or brother, and those were the only people she interacted with on a regular basis._ Damn, I need to convince Sakumo to let me out more._

"Is there a problem, Hatake-san?" Orochimaru sneered, emphasizing the suffix.

"I knew I shouldn't have let you watch my sister!" Sakumo seemed ready to cut him in two.

"Woah, woah!" Kumade held her hands up. "Relax, Sakumo. Orochimaru's been great! We've been working on math together, and he's been real careful, too! I'm still alive, aren't I?"

Though her brother wasn't happy, he did relax slightly. "Fine. Wait here. I'll bring the payment for the C-rank mission," said Sakumo stiffly.

"That's not necessary." Orochimaru stood up, gathering his books. "Goodbye, Kumade. Hatake-san." He brushed past Sakumo and shut the door without another word.

Her brother watched him go. "Good riddance. I don't know what I was thinking, asking him to babysit you." He promptly yelped when Kumade whacked him in the back of the head.

"You're the one who irritated him! I'll have you know that he was the best babysitter I've had!" She scowled at him. "And I don't need a babysitter."

"I can't help it," he whined. "He's just so annoying! And he was disrespecting you, too."

Kumade gave him a flat look. "What?"

"He didn't use a suffix with you, remember?"

"I don't use a suffix with you, either," she pointed out.

"That's not the same thing! I'm your brother!"

Kumade snorted. "How would I know that it'd be different? How many people do I talk to, besides you and the babysitters?"

"Well, uh…" He scratched his head. "There's my teammates! And…"

She raised her eyebrows at him.

"Alright, you've got a point," conceded Sakumo. "When I'm home, I'll take you to different places."

"But you're never home!" she exploded. "I haven't seen the outside of this house in two weeks!" Kumade pinched the bridge of her nose and sighed. Slowly, she counted to three in her head. "Look, Sakumo. I get you want to keep me safe. But I'm in Konoha, for gods' sake! It's the safest place there is!" She sighed again and lowered her voice. "Keeping me cooped up inside this house isn't going to help me. Can you at least let me out of the house with a summon?"

Sakumo seemed both shocked and stricken by her outburst. After a long moment, he spoke. "Yeah." His voice was barely a murmur. "Yeah, you're right. I'll… I'll loosen the seal restrictions. I'll ask Tsunade and Mayu and Koharu-sensei, and…"

Impulsively, Kumade gave him a hug. "Thanks, Sakumo-nii. I'm glad you're back."

"Me too." He wrapped his arms around her. After their father's death, Sakumo and math had basically become her life. Orochimaru, in all his annoying glory, had reminded her that there was more to this wonderful, crazy new world. There were people and places and magic sealing chakra to explore. _I think I'm ready, now._

"But don't think you're off the hook." Kumade felt Sakumo stiffen. "We're inviting Orochimaru for dinner, and you're apologizing. After that, I'm getting more textbooks. And clothes."

"Dinner? Apologies!?" yelped Sakumo. After a second, he added a confused, "Clothing?"

It was uncharacteristic of her to ask for clothing, true. In both lives, Kumade was indifferent at best to her appearance. But even she had a limit. "Look at my clothing, brother."

Sakumo glanced down, and realization dawned. Her clothing was about a foot too small. "Oh." He suddenly looked very, very guilty.

"No harm done," she reassured him. "Just get me some clothes, and we'll call it even."

He pulled her into another hug. "I'm sorry, Kuma," murmured Sakumo into her ear. "I haven't been a very good brother, huh? I'll make up for it. I promise. It'll be better now."

Kumade closed her eyes and laughed softly. "Silly brother. Don't worry about me. I'll be fine."

"I mean it, Kumade!" His voice was desperate, almost pleading.

She rested her head on his shoulder. "I know you do."

* * *

**AN:** Kumade meets a brilliant teenager who she knows nothing about. In the story, several months have passed since her father's death. In the next chapter, she'll meet more familiar characters.

It's been over a year since I posted this story, and I'm sorry for taking so long. Thanks to everyone who reviewed. Your words were great encouragement. I really appreciate every follow, favorite, and review. I will do my best to reply to each one, though it may take a little longer.

Special thanks to **MalevolentRace**, who is an exceptional beta.


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